Comparative study on gamma-ray detectors for in-situ ocean radiation monitoring system

Applied radiation and isotopes : including data, instrumentation and methods for use in agriculture, industry and medicine(2023)

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Large-sized crystals and state-of-the-art photosensors are desirable to cope with low environmental radioactivity (e.g., 1-2 Bq center dot m(-3) Cs-137 in surface seawater) for homeland security purposes. We compared the performances of two different gamma-ray detector assemblies, GAGG crystal + silicon photomultiplier (SiPM) and NaI(Tl) crystal + photomultiplier tube, for our mobile in-situ ocean radiation monitoring system. We performed energy cali-bration, followed by water tank experiments with varying the depth of a(137)Cs point source. Experimental energy spectra were compared with MCNP-simulated spectra with identical setup and the consistency was validated. We finally assessed the detection efficiency and minimum detectable activity (MDA) of the detectors. Both GAGG and NaI detectors exhibited favorable energy resolutions (7.98 +/- 0.13% and 7.01 +/- 0.58% at 662 keV, respectively) and MDAs (33.1 +/- 0.0645 and 13.5 +/- 0.0327 Bq center dot mm(-3) for 24-h Cs-137 measurement, respectively). Matching the geometry of the GAGG crystal with that of the NaI crystal, the GAGG detector outperformed the NaI detector. The results demonstrated that the GAGG detector is potentially advantageous over the NaI detector in detection efficiency and compactness.
GAGG-SiPM detector,NaI(Tl)-PMT detector,In-situ ocean radiation monitoring,Spectrometers,MCNP simulation,Homeland security
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